The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In the prior art, the optical access network (collectively referred to as FTTx) is classified into Fiber To The Home (FTTH), Fiber To The Building (FTTB), Fiber To The Curb (FTTC) and the like, according to the location of the optical network unit (ONU).
The formal name of the optical access network (OAN) is fiber in the loop (FITL). Due to the high bandwidth, the OAN is capable of developing Triple Play in a better way, i.e., a service for simultaneously transmitting voices, data, and multimedia videos. The OAN mainly employs a passive optical network (PON) technology. As an emerging broadband access technology for covering the last mile, the PON does not need node equipments in an ODN, but only needs a simple optical splitter, which thus has advantages of saving fiber resources, high equipment security, high networking speed, and easy maintenance. In the buildings having subscribed the FTTH service, transmission resources can be conveniently obtained. Moreover, thanks to the high broadband property, the FTTH has become an effective supplementary means for 3G IP transmission base stations.
Currently, there are mainly two mainstream technologies that are relatively mature, namely, Ethernet passive optical network (EPON) and Gigabit passive optical network (GPON). A main network architecture of an FTTx network is shown in FIG. 1, which shows a network architecture of the OAN, and the specific OAN reference architecture is shown in FIG. 2.
The OAN is formed by a customer premises network (CPN), an access network, and a service node function (SNF). The main network elements of the CPN and the access network include: an optical line terminal (OLT), an optical distribution network (ODN), an optical network unit/optical network terminal (ONU/ONT), and an adaptation function (AF). In the access network, the AF is an optional device, which mainly provides a conversion between an ONU/ONT interface and a user network interface (UNI). The AF may also be built in the ONU, and in this case, a reference point a can be omitted. The AF may also be arranged behind the OLT to provide a conversion between an OLT interface and a service node interface (SNI). The AF may either be considered as a function of the CPN or a function of the access network, in which T is a reference point for the UNI interface, and V is a reference point for the SNI interface. The OLT provides a network interface for the ODN and is connected to one or more ODNs. The ODN provides a transmission means for the OLT and the ONU. The ONU provides a user side interface for the OAN and is connected to the ODN.
A customer premises equipment (CPE) is connected to the AF via the UNI interface (for example, a DSL line). Next, the AF converts a packet format from a format of the UNI interface into a format of an interface a (for example, an Ethernet link) capable of being connected to the ONU. Then, the ONU converts the packet into a format capable of being delivered on the ODN (for example, EPON encapsulation, or GPON encapsulation based on generic framing). Finally, the OLT converts the packet into a packet format of the SNI interface (for example, Ethernet link), and then accesses a service node.
The 3G/2G radio communication system employs a similar structure, which includes a radio access network (RAN) and a core network (CN). The RAN is adapted to process all the radio related functions, whereas the CN processes all the voice calls and data connections within the radio communication system, and implements the switching and routing functions with an external network. The CN is logically divided into a circuit switched (CS) domain and a packet switched (PS) domain. The RAN and the CN, together with a mobile station (MS), constitute the entire 3G/2G radio communication network, and the system reference architecture thereof is shown in FIG. 3.
A base station (BS) is called a base transceiver station (BTS) in GSM/GPRS/CDMA/CDMA2000, and it is called a Node B in WCDMA/TD-SCDMA. A base station controller (BSC) is called a radio network controller (RNC) in WCDMA. In CDMA2000, a packet control function (PCF) is located between the BSC and a packet data serving node (PDSN) and supports packet data services. As a part of the RAN, the PCF may be allocated together with the BSC or separately.
As for WCDMA, the UTRAN uses the lu serial interfaces, which includes lu, lur, and lub interfaces. Among such interfaces, the protocol stacks are classified into a corresponding radio network layer (RNL) and a transport network layer (TNL) according to the general protocol model at the UTRAN interface. The lu interface is an interface for connecting the UTRAN to the CN, which is an open standard interface with the RANAP as the control plane protocol and the GTP protocol as the user plane protocol. The lur interface is an interface for connecting one RNC with another, which is an exclusive interface for the UMTS system, and is adapted to mobile management of the MS in the RAN. For example, if a soft handover is performed between different RNCs, all data of the MS is transmitted from the RNC in operation to candidate RNCs via the lur interface. The lur interface is also an open standard interface with the RNSAP as the control plane protocol and the lur FP as the user plane protocol. The lub interface is an interface for connecting the Node B to the RNC, which is also an open standard interface, and takes the NBAP as the control plane protocol and the lub FP as the user plane protocol.
The Node B is a BS (i.e., a radio transceiver) for the WCDMA system, and includes a radio transceiver and a base band processing unit. The Node B is interconnected with the RNC via the standard lub interface and mainly adapted to complete the processing of the physical layer protocol at the Uu interface. The main functions of the Node B mainly lie in spreading, modulating, channel coding, despreading, demodulating, and channel decoding, as well as interconversion between the base band signal and the radio frequency (RF) signal.
The RNC is adapted to control the radio resources of the UTRAN and has the main functions of connection establishment, disconnection, handover, macro diversity combination, radio resource management and control. Particularly, the RNC includes the following functions: (1) the broadcast distribution and system access control; (2) the mobility management, such as handover and RNC relocation; and (3) the radio resource management and control, such as macro diversity combination, power control, and radio bearer distribution.
The radio interface protocol stack architecture between a user equipment (UE) and the UTRAN includes a plurality of protocols distributed and implemented in different nodes in the RAN. As shown in FIG. 4, a radio resource control (RRC) protocol is implemented in the UE and RNC, and mainly adapted to implement the RRC connection management, radio bearer management, paging/broadcasting, mobility management, and other functions. The RRC protocol is responsible for configuring parameter information of the other protocol entities in the radio interface protocol stack. A radio link control (RLC) protocol is implemented in the UE and the RNC, and mainly adapted to implement the data transmission function of user data and provides three data transmission modes respectively suitable for transmitting service data with different QoS requirements. A media access control (MAC) protocol is generally implemented in the UE and RNC and responsible for selecting suitable transmission formats for the user data and realizing the mapping from logical channels to transport channels. As for some special types of channels, the Node B supports the MAC protocol. A packet data convergence protocol (PDCP) is implemented in the UE and RNC and has the following functions. The PDCP protocol respectively performs header compression and decompression of the IP data stream in the transmitting and receiving entities, for example, the TCP/IP and RTP/UDP/IP header compression manners are corresponding to particular combinations of network layers, transport layers, or upper layer protocols. The PDCP protocol further has the function of user data transmission, that is, forwarding the PDCP-SDU from the non-access stratum to the RLC layer, in which if the lossless SRNS relocation function is supported, the PDCP-SDU and the corresponding serial number are forwarded, so as to multiplex a plurality of different RBs into the same RLC entity.
A broadcast/multicast control protocol (BMC) has the functions of storing broadcast messages of the cell, monitoring the traffic flow and requesting radio resources for a cell broadcast service (CBS), scheduling BMC messages, sending the BMC messages to the UE, transmitting the cell broadcast messages to a high layer (the NAS).
In the current protocol stacks, since the Node B merely processes the physical layer protocols, all self-adaptive technologies that are determined through using the resource management are required to be implemented in the RNC, and two stages are required from the network to the terminal, that is, from the RNC to the Node B, and from the Node B to the terminal, and vice versa. As a result, a long delay is generated at the lub interface, and the processing capacity of the Node B and the statistical-multiplexing rate of the transmission resources at the lub interface are both reduced. Due to the long delay at the lub interface, the throughput of the retransmission mechanism of the RLC layer between the RNC and the UE is lowered. What's worse, due to the long delay at the lub interface, the outer loop power control algorithm cannot rapidly adjust the SiRtarget according to changes of the airlink. Meanwhile, the cell load information relies on the periodical report from the Node B, so that the information hysteresis exists, and as a result, the load information obtained by the RNC is not in real time.
Therefore, the protocol structure with all the access high layers being allocated in the RNC is not suitable for high-speed data transmission, since such a protocol structure cannot guarantee high speed and high efficiency of the data transmission upon adopting the technologies similar to self-adaptive coordination and feedback control. Thus, it is difficult to meet the requirements of the high-speed data transmission.
A hybrid fiber-coaxial (HFC) access network (DOCSIS) is a bidirectional interactive broadband network based on the cable television coaxial network, which reserves the traditional analogue transmission mode and also makes full use of the current cable television coaxial cable resources, for providing various services for users such as phone calls, broadcasting and television, video on demand, Internet access, videoconference, and data, without allocating new distribution networks. Therefore, the DOCSIS possesses low cost, wideband, and multi-service properties, which will become a desirable solution for the last mile broadband access. The DOCSIS is a CableLabs standard for the bidirectional interactive HFC access network, and the PacketCable standard is a DOCSIS-based multi-service operator (MSO) broadband standard.
The PacketCable is divided into an HFC access network, a CPN, and a managed IP network, and the PacketCable reference architecture based on the HFC access network as shown in FIG. 5. The main network elements of the HFC access network and the CPN include: a cable modem terminal system (CMTS), an HFC transport network (HFC/Cable Network), a cable modem (CM), a multimedia terminal adapter (MTA) (omitted in the figure) and the like. The CMCI is a reference point for the CPE and the CM in the CPN; the CMRFI is a reference point between the CM and the HFC/Cable Network; and the CMTS-NSI is an Ethernet aggregation reference point between the CMTS and the managed IP network.
The managed IP network and the CPE can employ Layer 2 network bridging technology, and may also employ IP Layer 3 routing technology.
A transmission method for a 2G/3G network BS in the prior art is described as follow.
E1/T1 is taken as the transmission technology of the BS. For example, FIG. 6 is a schematic view of a typical WCDMA networking transmission mode. Referring to FIG. 6, a user leaves the E1 networking via the lub interface of the WCDMA. The WCDMA provides a maximum bandwidth of merely 2 Mbps for each user. The lub transmission of WCDMA R99 employs an ATM transmission technology. The ATM can be carried on the TDM transmission, for example, on the E1/T1 (E1 transmission rate is 2 MHz, and T1 transmission rate is 1.5 MHz). Generally, in order to support a great number of users, the BS needs to multilink bundle the E1/T1, i.e., employing an inverse multiplexing over ATM (IMA) technology.
In the prior art described above, when the transmission bandwidth required by the data service is continuously increased, if the operators still employ the E1/T1 transmission mode, the link load between the BS and the BSC is relatively heavy due to the slow transmission rate of the E1/T1 transmission mode, which cannot meet the transmission rate requirement of the high-speed data service, and cannot guarantee the QoS of the high-speed data service. Meanwhile, the low charge of the data service will result in high cost and low returns, thereby severely influencing the operators' profits.
Therefore, the radio network transmission has become an urgent problem to be solved by the operators. The operators are confronted with the selection of either establishing their own transmission networks or seeking other inexpensive alternative technologies.